1. Field of the Invention
The present invention relates generally to radioimmunodetection and radiotherapy of diseases such as cancer. More particularly, the present invention relates to the chemicals used in transporting radio-isotopes to the tumor or organ which is being imaged and/or treated.
2. Description of Related Art
There presently is great interest in the use of radioisotopes in gamma imaging and/or beta therapy of cancer. These procedures basically involve conjugating the radioisotope or radiometal to a tumor-specific or tumor-associated antibody. Upon administration to the vascular system, the antibody-radioisotope conjugate attaches only to the specific tumor of interest. Radioimaging or radiotherapy can then be accomplished at the tumor depending upon which radioisotope is used.
At the present time, radioimmunodetection of cancer is practiced using .sup.111 In, .sup.99m Tc, .sup.68 Ga and other short lived radioisotopes in combination with bifunctional organic molecules capable of chelating the radiometal ion and conjugating with a tumor-associated or tumor-specific antibody. While this imaging methodology is a potentially powerful tool, it has not yet been developed to the fullest extent possible The principal difficulty is the innate chemical instability of the organic chelates when subjected to the physiological conditions encountered in vivo. Thus, radiometals often break away from decomposed chelate and are deposited in the liver, spleen, bone marrow, etc. This decomposition of the organic chelates is undesirable because it not only reduces effectiveness of the treatment, but also prevents rapid excretion of excess radioisotopes from the body.
It would be desirable to provide improved chelate molecules which can be used to transport radiometals to specific tumors or organs without the problems of decomposition associated with the use of organic chelates.